The term “flexible cable,” as used herein, means any flexible, elongated, energy or fluid-conducting device, such as a cable composed of one or more electrical wires or optical fibers, a fluid-conducting hose for conducting compressed air or a hydraulic fluid used as a medium for transmission of motive power, a flexible conduit used to convey a gas, a liquid, or another fluid material for use in a machine or industrial process, a flexible actuator such as a Bowden wire, or a flexible rotating shaft with or without anon-rotating sheath. Such flexible cables are used, for example, to connect relatively moving parts of a machine such as a machine tool, an industrial robot, or a conveyor or other material-handling or material-carrying machine, such as a hoist or other machine used in a civil engineering application.
When a flexible cable is connected to a moving part, torsion, flexion, and tensile forces applied to the cable as a result of movement of the moving part can result in damage to, or distortion of, the cable. Cable guides have been used to avoid damage and distortion of the cables.
As shown in FIG. 7, a typical cable guide 100 is composed of a number of links, each comprising a pair of side plates 102 disposed on both sides of a cable C and connecting plates 101 connecting the side plates. As shown in FIG. 7, the connecting plates 101 are provided both above and below the cable, and together with the side plates 102, form an elongated channel through which the cable C extends. The side plates 102 on each side of the guide are hinged to one another so that the guide can bend at least in a single plane. Usually, the flexion of the guide is limited to a specific minimum radius of curvature in order to avoid kinking of the cable C.
Typically, the cable guide has a fixed end 105 and a moving end 106. Where a cable guide of sufficient length is folded on itself by a bend 120 as shown in FIG. 5, it is possible for two portions of the guide to come into face-to-face contact with each other. Friction between the contacting parts of the guide can obstruct smooth reciprocating motion. Moreover, frictional contact over time can cause wear and eventual breakage of the cable guide. Breakage can also result from interference between projecting portions of the two facing parts of the guide.
To avoid the problems resulting from frictional contact between facing parts of a folded cable guide, a skate can be interposed between the facing parts. As illustrated in FIG. 5, a skate 400 is sandwiched between two facing parts of the cable guide, preventing direct contact between the facing parts.
A typical conventional skate is depicted and described in United States Patent Application Publication 2005/0155337, dated Jul. 21, 2005.
As shown in FIG. 6, the conventional skate 400 includes a series of interconnected skate units in aligned, sequential relationship, each having a pair of side frames 430. Each side frame has an L-shaped cross-section, and is provided with pair of rollers 420 mounted on a vertical part of the frame. The rollers are positioned so that they can be sandwiched between the facing parts of the guide. The skate units are connected by connecting blocks 450, which maintain the side frames 430 at a fixed distance from each other. Adjacent units are fixed to the connecting blocks by bolts 440, which are threaded into screw holes in the connecting block 450.
The skate 400 is formed by connecting a suitable number of skate units to one another to provide a skate having a length corresponding to the maximum overlap of the two mutually facing parts of the guide. Because the skate units are fixed to the connecting blocks by bolts, and also because flanges of the side frames 430 underlie the connecting blocks, the entire skate is substantially inflexible. The conventional skate can be used satisfactorily if a sufficient portion of the cable guide adjacent the fixed end is always straight. However, if some bending occurs in the portion of the guide adjacent the fixed end, the skate may need to be shortened in order to avoid the generation of excessive forces that could result in deformation or breakage of the guide, or in impairment of the smooth operation of the guide.